Automatically set walletdb.spv according to client

[OrfeasLitos]

This PR obviates the need for manually setting the 'spv' property of walletdb when the 'client' property is provided. The property is set to the same value as the client node. The original, manual way of setting the spv property is maintained for backwards compatibility, for walletdbs without a client and for manually overriding the client mode.

[codecov-io]

Codecov Report

Merging #621 into master will increase coverage by 0.21%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #621      +/-   ##
==========================================
+ Coverage   53.32%   53.53%   +0.21%     
==========================================
  Files         104      109       +5     
  Lines       27666    27955     +289     
  Branches     4737     4748      +11     
==========================================
+ Hits        14752    14965     +213     
- Misses      12914    12990      +76

Impacted Files	Coverage Δ
lib/wallet/walletdb.js	75.78% <100%> (+0.3%)	⬆️
lib/node/spvnode.js	48.11% <0%> (ø)
lib/wallet/index.js	100% <0%> (ø)
lib/wallet/node.js	18.42% <0%> (ø)
lib/bcoin.js	97.26% <0%> (ø)
lib/wallet/client.js	13.2% <0%> (ø)
lib/blockchain/chain.js	60.83% <0%> (+0.27%)	⬆️
lib/net/hostlist.js	31.04% <0%> (+0.27%)	⬆️
lib/node/http.js	39.64% <0%> (+0.5%)	⬆️
... and 3 more

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[nodech]

This will crash on most common use case: WalletClient where wallet node runs separately, because WalletClient wont have node.

[OrfeasLitos]

It now checks whether the node exists before touching its spv filter.

[pinheadmz]

#532 Might be a better solution to this issue - it covers all three wallet/node configuration (plugin, separate process and testing suite), and in all cases chain.spv (bool) is accessible. We could add a line to #532 that sets walletDB.spv based on that client info, if no options.spv is set...

[OrfeasLitos]

Sounds good. Should I redo this PR against your PR so that we keep the regression test as well?

[pinheadmz]

Hm yeah, I have one more update I need to do on that PR, which will include a spv-test.js hopefully we can get that merged, then follow up with your feature, and merge your test into that one. Will probably have that ready in a few days

[OrfeasLitos]

Sounds good. Also take a look at #417, I've written an spvnode-test.js. It may be of help for your test.

[pinheadmz]

@OrfeasLitos Ok #749 is a cleaner PR that just exposes prune and spv properties to the wallet, whether it's running as a plugin or standalone. Only problem is the info is unavailable until walletDB.open() gets the details from chain (it has to make an API call to the node server if running in standalone mode) but I think you could insert your check in open() as well.